from wht ive heard the blackjack and Samsung i-760 have the same problem. This fix worked on my 760 so give it a shot.
Download the file that i link, transfer the CAB to your blackjack and then run. save the seting that are already chosen, and reboot. Come back and let me know if this works.
http://www.liquidresults.net/pda/PdaApp.exe
all of the info for this is in this 6-7 page thread...
http://pdaphonehome.com/forums/samsung- ... ter-4.html